Nikos Nissiotis (1924-1986) was one of the foremost and formative intellectuals of the ecumenical movement in the twentieth century. As professor of philosophy and psychology of religion at the University of Athens, director of the Bossey Institute, and Chairman of the Faith and Order Commission of the World Council of Churches, he interpreted the Orthodox spiritual tradition for a Western audience and highlighted the role of Christian thought in the modern world. This collection of his most fundamental and significant articles - some of which have been largely inaccessible until now - includes an introduction by the editors to the ecumenical and theological legacy of this exceptional thinker.